1. Field of the Invention
The present invention relates to an ink jet ink, an ink cartridge by using the above-described ink, and an ink jet recording method.
2. Description of the Related Art
Regarding an image recorded on a recording medium by using a pigment ink, a phenomenon in which the image is observed to take on a color different from the color intrinsic to the pigment recorded in the image depending on the angle of observation of the image (bronze phenomenon) occurs. An occurrence of this is attributable to difference in refractive index depending on a wavelength in a visible light region when light is refracted at the surface of a pigment layer constituting an image.
In order to solve the bronze phenomenon, methods in which inorganic fine particles or water-insoluble polymer fine particles are contained in a pigment ink have been proposed previously (refer to Japanese Patent Laid-Open No. 2005-179482 and Japanese Patent Laid-Open No. 2008-63500). Japanese Patent Laid-Open No. 2005-179482 discloses that a bronze phenomenon of an image is improved by further containing a titanium dioxide pigment serving as inorganic fine particles in a pigment ink. Japanese Patent Laid-Open No. 2008-63500 discloses that a bronze phenomenon and glossiness of an image are improved by an aqueous pigment ink containing water-insoluble cross-linked polymer particles. Furthermore, a method by using a core-shell type pigment, in which pigment particles are covered with a water-insoluble polymer has been proposed (refer to Japanese Patent Laid-Open No. 2008-88427). Japanese Patent Laid-Open No. 2008-88427 discloses that a bronze phenomenon and glossiness of an image are improved by an ink containing a core-shell type pigment covered with a water-insoluble cross-linked polymer. These methods suppress variations in refractive index at an image surface through the use of the fact that the surface refractive indices of inorganic fine particles and a water-insoluble polymer exhibits no dependence on wavelength and, therefore, these fine particles are present in such a way as to surround pigment particles when an image is formed.